BACKGROUND AND PURPOSE: The Albumin in Acute Stroke (ALIAS) Part 2 Trial is directly testing whether 2 g/kg of 25% human albumin (ALB) administered intravenously within 5 hours of ischemic stroke onset results in improved clinical outcome. Recruitment into Part 1 of the ALIAS Trial was halted for safety reasons. ALIAS Part 2 is a new, reformulated trial with more-stringent exclusion criteria. Our aim was to explore the efficacy of ALB in the ALIAS Part 1 data and to assess the statistical assumptions underlying the ALIAS Part 2 Trial. METHODS: ALIAS is a multicenter, blinded, randomized controlled trial. Data on 434 subjects, comprising the ALIAS Part 1 subjects, were analyzed. We examined both the thrombolysis and nonthrombolysis cohorts combined and separately in a "target population" by excluding subjects who would not have been eligible for the ALIAS Part 2 Trial; the latter comprised patients >83 years of age, those with elevated baseline troponin values, and those with in-hospital stroke. We examined the differences in the primary composite outcome, defined as a modified Rankin Scale score of 0 to 1 and/or a National Institutes of Health Stroke Scale score of 0 to 1 at 90 days after randomization. RESULTS: In the combined thrombolysis plus nonthrombolysis cohorts of the target population, 44.7% of subjects in the ALB group had a favorable outcome compared with 36.0% in the saline group (absolute effect size=8.7%; 95% CI, -2.2% to 19.5%). Among thrombolyzed subjects of the target population, 46.7% had a favorable outcome in the ALB group compared with 36.6% in the saline group (absolute effect size=10.1%; 95% CI, -2.0% to 20.0%). CONCLUSIONS: Preliminary results from the ALIAS Part 1 suggest a trend toward a favorable primary outcome in subjects treated with ALB and support the validity of the statistical assumptions that underlie the ALIAS Part 2 Trial. The ALIAS Part 2 Trial will confirm or refute these results. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov/ALIAS. Unique identifier: NCT00235495.